Process for increasing the storing capacity of undressed mineral tanned leather



Patented F b. 5, 1 35 UNITED STATES OFFlCE PROCESS FOR INCREASING THE STORING CAPACITY OF TANNED LEATHER Rudolf Sajitz, Berlin,

Chemische Fabrik Po Pirna-Copitz, German As is known, mineral-tanned leather, intended for further working up, cannot be kept or stored for lengthy periods, even in the wet state (for instance chrome leather only 2 to 3 days), without its condition being impaired to a great extent in various respects, for instance as regards color. This has been experienced in practice as a severe disadvantage, as chrome leather cannot be either stored or sent away in unfinished state, as for instance is customary in the case of barktanned leather, and whereby the chrome-fineleather industry is enormously handicapped from the point of view of meeting varying tastes, as regards colour and dressingwithin the shortest possible period. Hitherto, one has occupied oneself with manifold suggestions as to how this disadvantage could be remedied, for instance how one could give mineral-tanned leather more or less storing capabilities in half-finishedstate' without unfavourable alteration; however, all en-' deavours in this direction were not crowned with success. I

It has now been found, that the desired storing capabilities of mineral-tanned leather may be attained by treating the same with relatively easily water-soluble substances, which not only leave the pH-value in the leather unimpaired, but, keep it at the height which it shows at the commencement of this. treatment. For this purpose all substances are adapted which hinder the decomposition of chrome compounds in the chrome leather, or at least can retard such decomposition for a long period. Apparently the above-named impossibility of storing mineral tanned, especially chrome-tanned leather, for a long period without the properties of such leather being injured, is due to a decomposition of the metal-compounds contained in the same. If however, substances are added to the already tanned leather, which possess the above-mentioned properties, this disadvantage will be'safely avoided.

Substances which are especially suited for the purpose in question are for instance waters'oluble carbohydrates, neutral alkali salts of simple and condensed aromatic sulfo acids, which are produced by sulfonating aromatic hydrocarbons, their homologues and condensation-products with carbonyl-compounds. Particularly favourable results are obtained-by making use of mixtures of the substances named, for example 'mixturesof carbohydrates, fat substances and a suitable solvent or of sulfo acids, carbohydrates anda suitable solvent.

UNDRESSED follows MINERAL Germany, assignor to M; & 00. G. in. b. IL, 5

No Drawing. Application August 22, No. 387,784. In Germany August 9 Claims. (01. 149-6) 1929, Serial 23, 1 28 Examples for execution 1. Chrome-tanned, moist leather is allowed to hang in a 5% solution of sodium benzol-sulfonate until it is thoroughly permeated by the same, which requires from to of an hour in an agitated bath, and .from 3 standing bath, according tothe leather. Thereupon the leather is well stretched, and may now be stored either in the moist or dried state for any desired length of time without its color and dressing. capability being influenced.

2. Chrome-tanned, moist leather is treated in a 5% solution of naphthalene-2,6-disulfonate of sodium according to Example 1.

3. Chrome-tanned, moist leather is treated in a solution of 5 kilos dinaphthylmethane-disulfonate of sodium and 2 kilos of Turkey red oil in litres of water, according to Example 1.

4. Chrome-tanned, moist leather is treated in a solution of 5 kilos of and 2 kilos Turkey redoil in 100 litres of Water according to Example 1.

As regards alum-tanned leather, the circumstances are different, inasmuch as this leather has to be stored dry for some time in order to be able to dye and dress it later. This storing capability is however temporally limited, for exthickness of the ample, alum-tanned leather which has been in stock for exactly 4 weeks, oifers dyeing, although this storing, or is prescribed. Longer storing, as about 2 to 3 months, alters the leather to such an extent that it is impossible to dye it evenly, even with the aid of approved expedients. This difiiculty is overcome if immediately after tanning, before ageing, the leather is treated as diificulties in ageing period 5. Alum-tanned, unaged leather istreated in a solution of 5 kilos of alpha-naphthalene-sulfonate of sodium and 3 kilos of Turkey red oil in 100 litres of water according to Example 1, dried, and can be then stored for any desired length of time.

I claim:

l. A process of treating mineral tanned moist leather, in order to make the same storable without affecting the colorability or the dressing capability of the same, consisting in conserving the pH-value of the leather by impregnating the same.with about 5% of a, mixture of equal parts of neutral alkali salts of aromatic sulfo acids and other soluble carbohydrates than alkyl cellulose.

2. A process of treating mineral tanned moist leather, in order to make the same storable without affecting the colorability or the dressing to 6 hours in. a.

capability of the same,

consisting in conserving the pH-value of the leather by impregnating the same with about 5% of a mixture of equal parts of neutral alkali salts of aromatic sulfo acids and other soluble carbohydrates than alkyl cellulose together with a solvent..

3. A process of treating mineral tanned moist leather, in order to make the same storable without affecting the colorabilityor the dressing capability of the same, consisting in conserving the pH-v'alue of the leather by impregnating the same with about 5% of a mixture of equal parts of neutral alkali saltsof aromatic sulfo acids, other soluble carbohydrates than alkyl cellulose and fatty substances together with a solvent.

4. As an article of manufacture, unfinished mineral tanned moist leather which is impregnated with about 5% of a mixture of equal parts of neutral alkali salts of aromatic sulfo acids,

other soluble carbohydrates than. alkyl cellulose and fatty substances.

5. A process oftreating mineral-tanned, moist leather, in order to make said leather storable without afiecting its properties of being subsequently colored or dressed, which process consists in suspending the moist leather in a 5% solution of sodium benzol-sulfonate until thoroughly permeated by such solution, and then stretching the leather.

6. A process of treating mineral-tanned, moist .leather, in order to make said leather storable without affecting its properties of being subsequently colored or dressed, which process con sists in impregnating the moist leather with a 5% solution of sodium benzol-sulfonate with reference to the pare weight until thoroughly permeated by such solution, and then stretching and drying the leather.

7. A process of treating mineral-tanned, moist leather, in order to make said'leather storable without affecting its properties of being subsequently colored or dressed, which process consists in suspending the moist leather in a solution" of about 5 kg. dinaphthyl-methane-disulphonate o sodium and about 2 kg. of Turkey-red oil in 100 liters of water for about to of an hour under agitation, and then stretching the leather. 8. A process of treating mineral-tanned, moist leather, in order to make said leather storable without afiecting' its properties of being subsequently colored or dressed, which process con- .sists in impregnating the moist leather with a solution of about 5 'kg. dinaphthyl-methanedisulphonate 'of sodium and about .2 kg. -of Turkey-red oil for each 100 kg. moist leather for about V2 to of an hour under agitation, and then stretching and drying the leather.

9. As an article of manufacture unfinished, mineral-tanned leather in moist state permeated with a solution in water of sodium benzol-sulionate and Turkey-red oil, the leather having the properties of being unimpaired by storing for a considerable time and of being subsequently 30 capable of coloring and dressing.

. RUDOLF SAJITZ. 

